Can anyone shed any light on this?
LadyStardust
Sorry to hear of your symptoms, but it doesn't sound like BPPV sometimes called "Crystals in the ear" characterised by your vision spinning round very fast as soon as you try to stand up which becomes impossible.
First time, the paramedics carted me off to hospital (I'm becoming a hospital addict!) suspecting a stroke, but despite a battery of scans nothing was found, but kept me in for a week.
As Blossoming says, it's caused by rapid head movements such that the "crystals" don't keep up. More likely to happen if you leap suddenly out of bed in the morning!
The second and last time it happened I stayed in bed, (living on my own) and it was 24 hours before I could stand up!
Didn't mean to put the wind up you because your situation is nothing like that, but it's worth being aware of BPPV.
Good Luck